Apparatus for treating the surface of an electrostatographic imaging

ABSTRACT

Apparatus for treating a surface of an electrostatographic imaging plate with a solid hydrophobic metal salt of a fatty acid comprising an electrostatographic imaging plate having a recyclicable imageable surface, means to support the imaging plate, fibrous treating means positioned adjacent to the imageable surface for pressure contact with the imageable surface, the fibrous treating means carrying on an outer surface thereof a transferable solid hydrophobic metal salt of a fatty acid and adapted to treat the imageable surface, and means to cause relative motion between the fibrous treating means and the imageable surface.

United States Patent Joseph [54] APPARATUS FOR TREATING THE SURFACE OFAN ELECTROSTATOGRAPHIC IMAGING [72] Inventor: Robert John Joseph,Penfield, N. Y. [73] Assignee: Xerox Corporation, Rochester, NY. [22]Filed: Sept. 2, 1969 [21] Appl. No.: 870,872

Related US. Application Data [62] Division of Ser. No. 594,249, Nov. 14,1966, Pat. No.

s2 U.S.C| ..1l8/637,l18/257,118/258 s1 rm. Cl. ..nos 1/14, BOSc 1/08 58FieldofSearch ..ll8/637, 257, 25s; 355/3;

[56] References Cited UNITED STATES PATENTS Carlson ..355/3 [451 May 23,1972 OTHER PUBLICATIONS Encyclopedia of Chemical Technology,"Kirk-Othmer, Vol. V, pp. 206- 208, 210, and 21 1. Received in ScientificLibrary, June 21, 1950. Encyclopedia of Chemical Technology" SecondEdition, Kirk-Othmer, Vol. I, pp. 2, 8 and 9. Received in ScientificLibrary, June 17, 1963.

Primary Examiner-John P. McIntosh AttomeyStanley Z. Cole and James J.Ralabate [57] ABSTRACT Apparatus for treating a surface of anelectrostatographic imaging plate with a solid hydrophobic-metal salt ofa fatty acid comprising an electrostatographic imaging plate having a vV recyclicable imageable surface, means to support the imaging I plate,fibrous treating means positioned adjacent to the imageable surface forpressure contact with the imageable surface, the fibrous treating meanscarrying on an outer surface thereof a transferable solid hydrophobicmetal salt of a fatty acid and adapted to treat the imageable surface,and means to cause relative motion between the fibrous treating meansand the imageable surface.

8 Claims, 2 Drawing figures PATENTEDMAY 23 I972 INVENTOR. ROBERT J.JOSERH BY E E IF/G1 2 ATTORNEY APPARATUS FOR TREATING THE SURFACE OF ANELECTROSTATOGRAPI-IIC IMAGING This is a division of application Ser. No.594,249, new U.S. Pat. No. 3,501,294, filed in the United States on Nov.14, 1966.

This invention relates in general to imaging systems, and

more particularly, to improved treating and cleaning devices, theirmanufacture and use.

The formation and development ,of images on the surface ofphotoconductive materials by electrostatic means is well known. Thebasic xerographic process, as taught by C. F. Carlson in U.S. Pat. No.2,297,691, involves placing a uniform electrostatic charge on aphotoconductive insulating layer, exposing the layer to a light andshadow image to dissipate the charge on the areas of the layer exposedto the light and developing the resulting latent electrostatic image bydepositing on the image a finely divided electroscopic material referredto in the art as toner. The toner will normally be attracted to thoseareas of the layer which retain a charge, thereby forming a toner imagecorresponding to the latent electrostatic image. This powder may then betransferred to a support surface such as paper. The transferred imagemay subsequently be permanently affixed to a support surface as by heat.Instead of latent image formation by uniformly charging thephotoconductive layer and then exposing the layer to a light and shadowimage, one may form the latent image by directly charging the layer inimage configuration. Other suitable fixing means such as solvent orover-coating treatment may be substituted for the foregoing heat fixingstep. Several methods are known for applying electroscopic particles tothe latent electrostatic image to be developed.

One development method as disclosed by E. N. Wise, in U.S. Pat. No.2,618,552, is known as cascade development. In this method, a developermaterial comprising relatively large carrier particles having fine tonerparticles electrostatically coated thereon is conveyed to and rolled orcascaded across the electrostatic image-bearing surface. The composition of the carrier particles is so chosen as to triboelectricallycharge the toner particles to the desired polarity. As the mixturecascades or rolls across the image-bearing surface, the toner particlesare electrostatically deposited and secured to the charged portion ofthe latent image and are not deposited on the uncharged or backgroundportions of the image. Most of the toner particles accidentallydeposited in the background areas are removed by the rolling carrier,due apparently, to the greater electrostatic attraction between thetoner and the carrier than between the toner and the dischargedbackground. The carrier and excess toner are then recycled. This resultsin excellent toner line images with relatively few toner particles inthe background portions.

Another method of developing electrostatic images is the magnetic brush"process as disclosed, for example, in U.S. Pat. No. 2,874,063. In thismethod, a developer material containing toner and magnetic carrierparticles is carried by a magnet. The magnetic field of the magnetcauses alignment of the magnetic carriers into a brush-likeconfiguration. This magnetic brush is engaged with the electrostaticimage-bearing surface and the toner particles are drawn from the brushto the latent image by electrostatic attraction. Still another techniquefor developing electrostatic latent images is the powder cloud processas disclosed by C. F. Carlson in U.S.

Pat. No. 2,221,776. In this method, a developer material comprisingelectrically charged toner particles in a gaseous fluid is passedadjacent the surface bearing the latent electrostatic image. The tonerparticles are drawn by electrostatic attrac-, tion from the gaseousfluid to the latent image. This process is particularly useful incontinuous tone development.

Any other development such as Touchdown development, as disclosed by C.R. Mayo in U.S. Pat. No. 2,895,847, may be used where suitable.

ln automatic xerographic equipment it is conventional to employ axerographic plate in the form of a cylindrical drum which iscontinuously rotated through a cycle of sequential operations includingcharging, exposure, developing, transfer, and cleaning. The plate isusually charged with corona of positive polarity by means of a coronagenerating device of the type disclosed by L. E. Walkup in U.S. Pat. No.2,777,957 which is connected to a suitable source of high potential.After forming a powder image on the electrostatic latent image duringthe development step, the powder image is electrostatically transferredto a support surface by means of a corona generating device such as thecorona device mentioned above. In automatic equipment employing arotating drum, a support surface to which a powder image is to betransferred is moved through the equipment at the same rate asthe'periphery of the drum and contacts the drum at the transfer positioninterposed between the drum surface and the corona generating device.Transfer is effected by a corona generating device which imparts anelectrostatic charge to attract the powder image from the drum to thesupport surface. The polarity of charge required to efi'ect imagetransfer is dependent upon the visual form of the original copy relativeto the reproduction and the electroscopic characteristics of thedeveloping material employed to effect development. For example, where apositive reproduction is to be made of a positive original, it isconventional to employ a positive polarity corona to effect transfer ofa negatively charged toner image to the support surface. When a positivereproduction from a negative original is desired, it is conventional toemploy a positively charged developing material which is repelled by thecharged areas on the plate to the discharged areas thereon to form apositive image which may be transferred by negative polarity corona. Ineither case, a residual powder image usually remains on the plate aftertransfer. Before the plate may be reused for a subsequent cycle, it isnecessary that the residual image be removed to prevent ghost images"from forming on subsequent copies. In the positive-to-positivereproduction process described above, the residual developer powder istightly retained on the plate surface by a phenomenon that is not fullyunderstood but believed caused by an electrical charge that preventscomplete transfer of the powder to the support surface, particularly inthe image areas. This charge is substantially neutralized by means of acorona generating device prior to contact of the residual powder imagewith a cleaning device. The neutralization of the charge enhances thecleaning efficiency of the cleaning device.

Typical electrostatographic plate cleaning devices include the brushtype cleaning apparatus and the web type cleaning apparatus. A typicalbmsh cleaning apparatus is disclosed by L. E. Walkup et al. in U.S. Pat.No. 2,832,977. The brush type cleaning means usually comprises one ormore rotating brushes which brush residual powder from the plate into astream of air which is exhausted through a filtering system. Thesebrushes may be treated with small amounts of oils such as hydrocarbonoils, waxes, silicone oils and the like to control the conductivity ofthe brush thereby rendering the brush more conductive or morenon-conductive, as desired.

However, in most cases, the brushes are normally untreated andgrease-free prior to use. The grease and similar material are usuallyremoved with conventional dry cleaning solvents. A typical web cleaningdevice is disclosed by W. P. Graff, Jr. et al. in U.S. Pat. No.3,186,838. As disclosed by Graff, Jr. et al., removal of the residualpowder on the plate is effected by rubbing a web of fibrous materialagainst the plate surface. These inexpensive and disposable webs offibrous material are advanced into pressure and rubbing or wipingcontact with the imaging surface and are gradually advanced to present aclean surface to the plate whereby substantially complete removal ofresidual powder from the plate is effected.

While ordinarily capable of producing good quality images, conventionaldeveloping systems suffer serious deficiencies in certain areas. Theelectrical and transfer characteristics of electrostatic image-bearingsurfaces are adversely affected when relative humidity is high. Becauseof the influence of various forces such as electrostatic and van derWall forces, many toner particles tend to form adherent deposits whichreduces the density of transferred images and impairs proper cleaning ofreusable imaging plates, belts, or drums. Numerous known carriers andtoners are abrasive in nature. Abrasive contact between toner particles,carriers, and imaging surfaces accelerates mutual deterioration of thesecomponents. Rubbing contact between cleaning devices and the imagingsurfaces also results in rapid erosion of the imaging surfaces. Attemptshave been made to protect the imaging surfaces with thin coatings suchas the coatings disclosed in US. Pat. No. 2,901,348 to Dessauer et a1.However, the protective overcoatings are merely temporary and eventuallyerode away leaving an unprotected imaging surface. Although thickcoatings would protect the imaging surfaces for longer periods of time,the electrical properties of the photoconductive layer impose certainlimitations as to the acceptable maximum thickness of the coating.Frequent replacement of deteriorated carriers and imaging plates isexpensive, inconvenient, and time consuming. Fines formed from theattrition of toner on rough imaging surfaces tend to drift and formunwanted deposits on critical machine parts. Electrostatographic copiesshould possess good line image contrast as well as acceptable solid areacoverage. However, when a process is designed to improve either lineimage contrast or solid area coverage, reduced quality of the other canbe expected. Attempts to increase image density by depositing greaterquantities of toner particles on the latent electrostatic image usuallyincrease undesirable background deposits. Further, for reasons not fullyunderstood, image quality is often impaired by the appearance of powderdeficient spots in the powder image. Thus, there is a continuing needfor a better system for developing latent electrostatic images.

It is, therefore, an object of this invention to provide a system whichovercomes the above noted deficiencies.

It is another object of this invention to provide a treatment systemwhich promotes transfer of toner particles from an electrostatic imagingsurface to a support surface.

It is a further object of this invention to provide a treatment systemwhich promotes transfer of toner particles in background areas of imagedsurfaces to carriers.

It is a further object of this invention to provide a treatment systemwhich promotes removal of toner particles from imaging surfaces bycleaning devices.

It is a still further object of this invention to provide a treatmentsystem which reduces mechanical abrasion of electrostatic imagingsurfaces.

lt is another object of this invention to provide a treatment systemwhich allows the employment of low electrostatic plate potentials.

It is a further object of this invention to provide a treatment systemwhich promotes the formation of dense toner images.

It is still another object of this invention to provide a treatmentsystem which reduces physical degradation of developing materials.

it is a still further object of this invention to provide a treatmentsystem which reduces or eliminates powder deficient spots.

It is another object of this invention to provide a treatment systemwhich continually maintains the electrical stability of electrostaticimaging surfaces. 1

It is another object of this invention to provide an electrostatographicsurface treatment system which provides electrostatographic surfaceshaving physical and chemical properties superior to those of knownelectrostatographic surfaces.

The above objects and others are accomplished, generally speaking, byproviding a system for continuously or intermittently treating reusableelectrostatographic surfaces with a.

stable solid hydrophobic salt of a fatty acid. Preferably, treatment iseffected with a device having a fibrous surface which is employed tosimultaneously clean and treat the reusable electrostatographic surface.The stable solid hydrophobic salt of a fatty acid may be carried on thetreatment surface of the treatment device of this invention in anysuitable form such as a loose powder, with a suitable binder, or as ahomogeneous film.

Excellent results have been obtained with zinc stearate, However, anysuitable stable aclid hydrophobic metal salt of a fatty acid may besubstituted for zinc stearate. The metal salt is preferablysubstantially insoluble in water. Water soluble metal salts lack theproper electrical properties and electrostatographic surfaces treatedwith such salts are adversely affected by humidity changes normallyoccurring in the ambient atmosphere. It should be noted however, that alarge proportion of salts normally regarded as insoluble actuallydissolve to a slight extent. To effectively carry out the purposes ofthis invention, the solubility of the salt should be negligible. Thesalts having the desired specific characteristics include many salts ofsaturated fatty acids, unsaturated fatty acids, partially hydrogenatedfatty acids, substituted fatty acids and mixtures thereof. Typical fattyacids from which stable solid hydrophobic metal salts may be derivedinclude: caproic acid, enanthylic acid, caprylic acid, pelargonic acid,capric acid, undecyclic acid, lauric acid, tridecoic acid, myristicacid, pentadecanoic acid, palmitic acid, magaric acid, stearic acid,nondecyclic acid, arachidic acid, behenic acid, stillingic acid,palmitoleic acid, oleic acid, ricinoleic acid, petroselinic acid,vaccenic acid, linoleic acid, linolenic acid, oleostearic acid, lieanicacid, parinaric acid, gadoleic acid, arachidonic acid, cetoleic acid andmixtures thereof. Typical stable solid metal salts of fatty acidsinclude: barium stearate, lead stearate, iron stearate, nickel stearate,cobalt stearate, copper stearate, strontium stearate, calcium stearate,cadmium stearate, magnesium stearate, zinc oleate manganese oleate, ironoleate, cobalt oleate, copper oleate, lead oleate, magnesium oleate,zinc palmitate, cobalt palmitate, copper palmitate, magnesium palmitate,aluminum palmitate, calcium palmitate, lead caprylate, lead caproate,zinc linoleate, cobalt linoleate, calcium linoleate, zinc ricinoleate,cadmium ricinoleate and mixtures thereof.

The stable solid hydrophobic metal salts of this invention may becarried by any suitable treatment device. In a preferred embodiment, thetreatment device comprises fibrous woven or non-woven webs. Fibrous websare preferred because maximum uniformity of treatment is achieved. Theconfiguration of the fibrous treatment device may be of any suitableshape such as in the form of a continuous web, cylinder or belt. 'Anysuitable fibrous material may be employed in the web, cylinder, or belt.Typical fiber material include furs, such as beaver fur, grey fox fur,rabbit fur, and the like; natural fibers such as cotton, wool, hair andthe like; and synthetic fibers such as nylon, cellulose derivatives andthe like; Any suitable coating method may be employed to apply the metalsalt to the treatment surfaces of the devices of this invention. Forexample, the stable solid hydrophobic metal salts may be applied as aloose powder, a melt, a solution, an emulsion, a dispersion or as acomponent in a film-forming binder composition.

The metal salt may be applied to the surface of the treatment device ofthis invention immediately prior to contact of the treatment surfacewith the imaging surface to be treated. Application may be controlled byemploying a dispenser which uniformly sprinkles the metal salt in theform of powder onto the treating surface while the treatment device isin operation in an imaging machine. Alternatively, the treatment surfacemay be provided with a supply of metal salt by rubbing a solid bar ofhydrophobic metal salt against the treatment surface. The metal salt barmay be formed by merely casting the metal salt in molten form in a mold,sintering particles of the metal salt or by binding metal salt particlestogether with a film-forming binder.

Further, where synthetic fibers are employed, the metal salts of thisinvention may be dispersed uniformly throughout the fiber during thefiber manufacturing process. When loose powder is employed, it may beapplied by merely sprinkling the powder onto the treatment surfaces ofthe device of this invention. Liquids containing the metal salt may beapplied to the treatment surface of this invention by any conventionalcoating method such as spraying or dip coating. The liquid may be afugitive or permanent material. When fugitive liquids are employed, theliquid is preferably a low boiling point liquid which may easily beremoved by conventional techniques after application. Generally, thenon-fugitive liquids employed in this invention are film-formingbinders. These film-forming binders may include natural resins,thermoplastic resins, and curable thermosetting resins. Typical naturalresins include: caoutchouc, colophony, copal, dammar, Dragons Blood,jalap, and the like. Typical thermoplastic resins include: thepolyvinyls and polyvinylidenes such as polystyrene, polymethyl styrene,polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinylalcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ethers, andpolyvinyl ketones; polyamides such as polycaprolactams andpolyhexamethylene adipamide; polyesters such as polyethyleneterephthalate; polyurethanes; polysulfides and the like. Typicaltherrnosetting resins include phenolic resins such asphenol-formaldehyde, phenol-furfural and resorcinol formaldehyde; aminoresins such as urea-formaldehyde and melamine-formaldehyde; polyesterresins; and the like.' The quantity of metal salt necessary to providethe improved results of this invention depends on many factors includingthe manner inwhich the salt is applied to the treating surface of thedevice of this invention, the relative velocities of the treatmentdevice surface and the electrostatographic surface being treated, thepressure employed to applythe metal salt to the electrostatographicsurfaces, the type of material employed in the treatment device (e.g.,length and number of fibers per unit area, and contact time between thetreatment device and the electrostatographic surfaces.) Generallyspeaking, satisfactory results are obtained whenfrom about 0.005 gramsto about 1 gram of metal salt per square foot is available at thetreatment surface of this invention immediately prior to contact withelectrostatographic imaging surface. Optimum results are obtained whenfrom about 0.01 to about 0.2 grams of metal salt is available at thetreatment surface because maximum physical degradation resistance,imaging surface cleanability and humidity insensitivity are achievedwith a minimum occurrence of background toner deposits.

Although the treatment device of this invention may be given the solefunction of treating the electrostatographic surface with solidhydrophobic salts of fatty acids, a combined cleaning and treatmentdevice is preferred, particularly in contact high speed copying machineswhere machine components requiring less space and having simplicity ofoperations are highly desirable.

The advantages of the improved device will become even further apparentupon consideration of the following disclosure of the invention,particularly when taken in conjunction with the accompanying drawingswherein:

FIG. 1 is a schematic illustration of an electrostatographic surfacetreating device according to one embodiment of this invention.

FIG. 2 is a schematic view of an electrostatographic surface treatingdevice according to another embodiment of thisinvention.

Referring now to FIG. 1, reference character designates a rotatablexerographic drum having an outer layer 12 of photoconductive insulatingmaterial such as vitreous selenium. The drum 10 is mounted to move inthe direction indicated by the arrow. The surface of drum 10'-isuniformly charged by a conventional corona charging device 14 andexposed to a pattern of activating electromagnetic radiation at 16. Thelatent electrostatic image formed by the exposure means 16 is developedby rotating drum 10 past the developing apparatus 17. In the developingapparatus 17, developing material is carried up by conveyor 14 andreleased onto chute l5 wherefrom it cascades down over the drum surface.After developing, most of the developed image is transferred at atransfer station 18 to a moving paper web 20. The transferred powderedimage may be permanently fixed to the web 20 by any conventional meanssuch as by the heat fuser 22. The drum 10 then passes through atreatment station 24 whereat the drum surface is simultaneously cleanedof the residual powder image and treated with a solid hydrophobic metalsalt thus completing the entire charging, exposing, developing,

transferring, cleaning and treatment cycle. At treatment station 24, aweb of treating material 26 is drawn from a rotatable supply wheel 28past dispenser means 29- for applying the metal salt to the webwherefrom it is continuously or intermittently advanced over a guideroll 30 into contact against the moving surface of drum 10. The web 26is usually advanced at a slower rate of movement than the movement rateof the drum surface, and preferably, although not necessarily, isadvanced in a direction substantially opposite to the direction of thedrum for the reasons described below. Rubbing contact of the web 26against the drum surface is incurred for a sufficient predeterminedlength of time during which the web 26 simultaneously removes theresidue of developing material from the drum l0 and treats the drumsurface with a solid hydrophobic metal salt of a fatty acid. Maximumefficiency in a minimum of time has been found to accrue when the web 26and drum 10 are moved in substantially opposite directions whereby theportion of the web 26 having the greatest concentration of metal saltcontacts the cleanest portion of .the drum surface. Thereafter the web26 continues advancing over a guide roll 32 and onto rotatable take-upreel 34. After the supply'of treatment material onsupply reel 28 hasbeen exhausted, the soiled web on take-up reel 34 may be. disposed ofand a fresh supply of material installed for continuance of operation.The rate at which a web of cleaning material is consumed is a functionof the relative rate of plate and web movement required to yieldsatisfactory cleaning. This has been found to vary to some degreedependent upon the particular cleaning material employed. 'It should beapparent that the ,most economical consumption rate will be the minimumweb velocity relative to the velocity of the plate at which goodcleaning is still obtained. For most materials tested, relative webvelocities were found to vary in the order of one-fortieth to oneone-hundredth of the plate velocity, or in other words, it is necessaryto present one clean inch of web to clean and treat every 40 to linearinches of electrostatographic plate surface.

In FIG. 2, another embodiment of the invention is shown wherein thecombination treatment-cleaner device having a brush type configurationis employed. Only the treatmentcleaning station 50 adjacent to a segmentof xerographic drum 52 is illustrated in FIG. 2. A cylinder 54 isprovided with a brush 56. The axial length of the cylinder 54isdependent upon the axial length of the xerographic drum 52. Apassageway generally designated as 58 extends from adjacent theperiphery of brush 56 through wall 60 of hood 61 and is adapted to admitan erodable plate 62 comprising a solid hydrophobic metal salt of afatty acid. The erodable plate 62 is fed through passageway 58 at apredetermined rate by means of a piston-gear rack combination 64 drivenby a plurality of worm gears 66. Ridges (not shown) runningperpendicular to the brush axis may be provided within passageway 58 torestrict plate 52 from passing freely through the passageway 58. Whenthe apparatus of FIG. 2 is utilized as a station in an automaticxerographic device, the cylinder 54 may optionally be constructed sothat the brush may be removed from contact with xerographic drum 52. Thepassageway 58 and erodable plate 62 are constructed so that they runalongv the entire axial length of cylinder 54. The erodable plate 62 ispositioned to compress the brush bristles along the exposed erodableplate edge. As each section of the brush is compressed by the edge oferodable plate 62, the individual fibers of the brush pick up minutequantities of the solid hydrophobic metal salt of a fatty acid andimmediately transfer at least a portion of the metal salt to thexerographic drum 52. Although it is not entirely clear, it appears thatthe bristles of the-brush tend to spring upright due to effects ofcentrifugal force immediately after compression along the edge oferodable plate 62. Since the inherent resilience of the bristles and theeffects of centrifugal force tend to cause the bristles to extendoutward after seems to facilitate the filling in and smoothing over ofmicroscopic scratches and imperfections present in the surface of drum52. In addition to wiping the surface of drum 52 with hydrophobic metalsalt material, the bristles also brush the residual powder image on thesurface of xerographic drum 52 into a current of air which is drawn bysuitable means (not shown) through outlet 68 of hood 61. Any particlesadhering to the brush may optionally be dislodged by bringing the brushinto contact with a rod 72. These dislodged particles are also carriedaway by the air exhausted through outlet 68. The edge of hood 61 isconstructed so as to be as close as possible to the surface of thexerographic drum 52 without making contact with the delicate surface.The negative pressure existing within ,hood 61 prevents toner particlesremoved from the xerographic drum surface from being expelled throughthe small opening that exists between the edge of the hood and thexerographic drum surface.

A relatively high brush speed is preferred for rapid and thoroughtreatment and cleaning. However, various factors at feet the particularperipheral brush speed to be employed. These factors include the type ofpowder material being removed from the xerographic. drum surface, thebrush material being used, the area of contact between the brush and thexerographic drum surface, the relative speed between the plate surfaceand the brush periphery, the electrostatic attraction remaining betweenthe residual powder and the xerographic drum surface and other relatedfactors. Generally, a minimum peripheral brush velocity of about feetper second is preferred because more effective cleaning and treatment isachieved.

Although the embodiments illustrated in the drawings depict theemployment of the treatment apparatus of this invention as a combinedtreatment device and cleaning device, it is apparent that the treatmentdevice may be employed solely as a treatment device. For example, thetreatment device may be positioned in the imaging cycle immediatelyafter the cleaning cycle.

The fundamental mechanism or mechanisms upon which the improved humidityresistance, better transfer performance, reduced plate abrasion, andelimination of powder deficient spots can be based have not been clearlyestablished. It is postulated, however, that factors which contribute tothe above described improvements include the continuous or intermittentformation of an ultra thin hydrophobic protective film on the surface ofthe electrostatographic imaging surface which stabilizes the electricalproperties of the electrostato graphic imaging surface; the filling inof any fine scratches present in the imaging surface; the reduction offriction during the development and cleaning processes; and thereduction of van der Waal forces between the toner particles and theimaging surface. When the solid hydrophobic metal salts of thisinvention are employed in the form of finely divided particles, theparticular salt employed is preferably transparent or light colored forconventional black on white copying systems because any stray metal saltparticle transferred to a copy sheet with the black powder image issubstantially invisible thereon.

The following examples further specifically define and describe thesystem of the present invention for treating electrostatographicsurfaces with solid hydrophobic metal salts of fatty acids. Parts andpercentages are by weight unless otherwise indicated. The examples beloware intended to illustrate the various preferred embodiments forcarrying out the invention.

EXAMPLEI A comparative test is conducted with apparatus similar to thatillustrated in FIG. 1. In the test, about one part colored styrenecopolymer toner particles having an average particle size of about 10 toabout 20 microns and about 99 parts coated carrier particles having anaverage particle size of about 600 microns is cascaded across anelectrostatic imagebearing surface. The developed image is thentransferred by electrostatic means to a sheet of paper whereon it isfused by heat. The residual powder is removed with a continuous webcomprising rayon and cotton fibers manufactured by Chipepee Mills, Inc.,Milltown, NJ. One-half the web is untreated and the other half is dustedwith zinc stearate having a particle size distribution from about 0.5microns to about 40 microns. The excess powder deposited is removed bymerely inverting the web and gently shaking it. After the copyingprocess is repeated 1,500 times, the copies and electrostatic imagingsurface are examined for quality and wear, respec-' tively. The portionof the copy images associated with the treated web side of the machinepossess markedly superior character definition and less background'thancopy images obtained on the untreated web side of the machine. Further,

micrograph studies of the imaging surface reveal substantially.

less wear on the side in contact with the treated portion of the webthan on the side in contact with the untreated portion of the web.

EXAMPLE II The procedure of Example I is repeated except that cobaltpalmitate having a particle size distribution from about 0.75 microns toabout 50 microns is substituted for the zinc stearate particles. Afterthe copying process is repeated 1,500 times, the copies andelectrostatic imaging surface are examined for quality and wear,respectively. The portion of the copy images associated with the treatedweb side of the machine possessed superior character definition and lessbackground than copy images obtained on the untreated side of themachine. Further, micrograph studies of the imaging surface revealsubstantially less wear on the side in contact with the treated portionof the web than on the side in contact with the untreated portion of theweb.

EXAMPLE III The procedure of Example I is repeated except that thetreated half of the cleaning web is impregnated with a 10 percentdispersion of finely divided particles of zinc stearate in anitrocellulose solution. About 0.05 grams of dispersion solids isdeposited on every 2 square feet of the treated portion of the web.After the copying process is repeated 1,500 times, the copies andelectrostatic imaging surface are examined for quality and wear,respectively. The portion of the copy images associated with the treatedside of the machine possess better character definition and lessbackground than copy images obtained on the untreated web side of themachine. Further, micrograph studies of the imaging surface revealsubstantially less wearon the side in contact with the treated portionof the web than on the side in contact with the untreated portion of theweb.

EXAMPLE IV dies of the imaging surface reveal substantially less wear onv the side in contact with the treated portion of the web than on theside in contact with the untreated portion of the web.

EXAMPLE V A comparative test is conducted with apparatus similar to thatillustrated in FIG. 1. The entire test is conducted in a humiditychamber at about F. and about 80 percent relative humidity. About 1 partcolored styrene copolymer tonerparticles having an average particle sizeof about 10 to about 20 microns and about 99 parts coated carrierparticles having an average particle size of about 600 microns iscascaded across an electrostatic image-bearing surface. The developedimage is then transferred by electrostatic means to a sheet of paperwhereon it is fused by heat. The residual powder is removed with acontinuous web comprising cotton fibers. One-half the web is untreatedand the other half is dusted with zinc stearate having a particle sizedistribution from about,0.5 microns to about 40 microns. The excesspowder deposited is removed by merely inverting the web and gentlyshaking it. After the copying process is repeated 1,500 times, thecopies and electrostatic imaging surface are examined for quality andwear, respectively. The portion of the copy images associated with thetreated web side of the machine possess superior character definition,greater image density and less background than copy images obtained onthe untreated web side of the machine. Further, micrograph studies ofthe imaging surface reveal substantially less wear on the side incontact with the treated portion of the web than on the side in contactwith the untreated portion of the web.

EXAMPLE VI The procedure of Example V is repeated except that thetreated side of the cleaning web is impregnated with a mixturecomprising 10 parts lead caprylate, 25 parts urea-formaldehyde resin and30 parts of nitrocellulose dissolved in methyl isobutyl ketone. About I0.02 grams of dispersion solids is deposited on about every 2 squarefeet of the'treated side of the cleaning web. After the copying processis repeated 1,500 times, the copies and electrostatic imaging surfaceare examined for quality and wear, respectively. The portion of the copyimages associated with the treated web side of the machine possesssuperior character definition and less background than copy imagesobtained on the untreated web side of the machine. Further, micrographstudies of the imag ing surface reveal substantially less wear on theside in contact with the treated portion of the web than on the side incontact with the untreated portion of the web.

EXAMPLE VI] A control run is made with apparatus similar to thatillustrated in FIG. 2 except that the fur brush is not treated with asolid hydrophobic metal salt of a fatty acid. About one part coloredstyrene copolymer toner particles having an average particle size ofabout 10 to about 20 microns and about 99 parts coated carrier particleshaving an average particle size of about 600 microns is cascaded acrossan electrostatic imagebearing surface. The developed image is thentransferred by electrostatic means to a sheet of paper whereon it isfused by heat. The residual powder is removed with a cylindrical furbrush manufactured from rabbit fur. The brush cylinder has a diameter ofabout 5 inches and is rotated at a linear velocity of about 25 linearfeet per second. After the copying process is res ctively. The copiespossess markedly superior character de nition, greater so ld areadensity and less background than the copy images obtained in the ExampleVi]. Further, micrograph studies of the imaging surface revealssubstantially fewer scratches than the imaging surface employed inExample VII.

The expression electrostatographic plate" as employed herein is intendedto include fiat plates, cylinders, and continuous belts.

Although specific components, proportions and procedures have beenstated in the above description of the preferred embodiments of thenovel treatment system, other suitable materials, as listed above, maybe used with similar results. Further, other materials and proceduresmay be employed to synergize, enhance or otherwise modify the novelsystem.

Other modifications and ramifications of the present invention willoccur to those skilled in the art upon a reading of the disclosure.These are intended to be included within the scope repeated 20,000times, the copies and electrostatic imaging EXAM PLE VIII The procedureof Example Vll is repeated except that the edge of a plate of sinteredzinc stearate particles is maintained in contact with the rotating furbrush during the cleaning process. The edge of the zinc stearate plateis positioned to compress the brush hairs immediately prior to contactwith the electrostatic latent image-bearing surface. After the copy ingprocess is repeated 22,000 times, the copies and electrostatic imagingsurface are examined for quality and wear,

of this invention.

What is claimed is:

1. An apparatus for treating a surface of an electrostatographic imagingplate with a solid hydrophobic metal-salt of a fatty acid comprising anelectrostatographic imaging plate having a recyclicableelectrostatically imageable surface, means to support saidelectrostatographic imaging plate, fibrous treating means positionedadjacent to aid electrostatically imageable surface for pressure contactwith said electrostatically imageable surface,'said fibrous treatingmeans carrying on at least an outer surface thereof adjacent saidelectrostatically imageable surface a transferrable solid hydrophobicmetal salt of a fatty acid, said fibrous treating means adapted to treatsaid electrostatically imageable surface with said solid hydrophobicmetal salt of said fatty acid, and means to cause relative motionbetween said fibrous treating means and said electrostatically imageablesurface.

2. An apparatus according to claim 1 wherein said fibrous treating meanscomprises a rotatably mounted cylindrical brush means.

3. An apparatus according to claim 2 wherein means are provided forapplying said solid hydrophobic metal salt of said fatty acid to saidbrush means prior to contact between said brush means and said imageablesurface.

4. An apparatus for treating a surface of an electrostatographic imagingplate with a solid hydrophobic metal salt of a fatty acid comprising anelectrostatographic imaging plate having a recyclicableelectrostatically imageable surface, means to support saidelectrostatographic imaging plate, a web positioned adjacent to saidelectrostatically imageable surface for pressure contact with saidelectrostatically imagea ble surface, said web carrying on at least anouter surface thereof adjacent said electrostatically imageable surfacea transferrable solid hydrophobic metal salt of a fatty acid, said webadapted to treat said electrostatically imageable surface with saidsolid hydrophobic metal salt of said fatty acid, and means to causerelative motion between said web and said electrostatically imageablesurface.

5. An apparatus according to claim 4 including means to intermittentlymove said web relative to said electrostatically imageable surface.

6. An apparatus according to claim 4 including means to apply said solidhydrophobic metal salt of said fatty acid to said web prior to contactbetween said web and said electrostatically imageable surface.

7. An apparatus according to claim 4 including means to load said webwith said solid hydrophobic metal salt of said fatty acid by rubbing asolid bar of said solid hydrophobic metal salt of said fatty acidagainst said web.

8. An apparatus according to claim 4 wherein said web comprisessynthetic fibers and said solid hydrophobic metal salt of said fattyacid is dispersed throughout said synthetic fibers.

l l i i

1. An apparatus for treating a surface of an electrostatographic imaging plate with a solid hydrophobic metal salt of a fatty acid comprising an electrostatographic imaging plate having a recyclicable electrostatically imageable surface, means to support said electrostatographic imaging plate, fibrous treating means positioned adjacent to aid electrostatically imageable surface for pressure contact with said electrostatically imageable surface, said fibrous treating means carrying on at least an outer surface thereof adjacent said electrostatically imageable surface a transferrable solid hydrophobic metal salt of a fatty acid, said fibrous treating means adapted to treat said electrostatically imageable surface with said solid hydrophobic metal salt of said fatty acid, and means to cause relative motion between said fibrous treating means and said electrostatically imageable surface.
 2. An apparatus according to claim 1 wherein said fibrous treating means comprises a rotatably mounted cylindrical brush means.
 3. An apparatus according to claim 2 wherein means are provided for applying said solid hydrophobic metal salt of said fatty acid to said brush means prior to contact between said brush means and said imageable surface.
 4. An apparatus for treating a surface of an electrostatographic imaging plate with a solid hydrophobic metal salt of a fatty acid comprising an electrostatographic imaging plate having a recyclicable electrostatically imageable surface, means to support said electrostatographic imaging plate, a web positioned adjacent to said electrostatically imageable surface for pressure contact with said electrostatically imageable surface, said web carrying on at least an outer surface thereof adjacent said electrostatically imageable surface a transferrable solid hydrophobic metal salt of a fatty acid, said web adapted to treat said electrostatically imageable surface with said solid hydrophobic metal salt of said fatty acid, and means to cause relative motion between said web and said electrostatically imageable surface.
 5. An apparatus according to claim 4 including means to intermittently move said web relative to said electrostatically imageable surface.
 6. An apparatus according to claim 4 including means to apply said solid hydrophobic metal salt of said fatty acid to said web prior to contact between said web and said electrostatically imageable surface.
 7. An apparatus according to claim 4 including means to load said web with said solid hydrophobic metal salt of said fatty acid by rubbing a solid bar of said solid hydrophobic metal salt of said fatty acid against said web.
 8. An apparatus according to claim 4 wherein said web comprises synthetic fibers and said solid hydrophobic metal salt of said fatty acid is dispersed throughout said synthetic fibers. 